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David A. Kofke - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic properties of supercritical co2 ch4 mixtures from the Virial Equation of state
Journal of Chemical & Engineering Data, 2016Co-Authors: Shu Yang, Andrew J. Schultz, David A. KofkeAbstract:Mixture Virial coefficients to seventh order are presented for the system CO2/CH4 at four supercritical temperatures: 323.15, 373.15, 473.15, and 573.15 K. Values are evaluated via the Mayer sampling Monte Carlo method using a three-site TraPPE model for CO2 and a one-site model for CH4. The coefficients are used to compute seven thermodynamic properties (viz., compressibility factor, isothermal compressibility, volume expansivity, isochoric and isobaric heat capacities, Joule–Thomson coefficient, and speed of sound) as a function of mole fraction and density for these temperatures. Comparison is made with corresponding data in the literature as obtained by molecular dynamics simulation, covering densities up to about twice the critical density. Key conclusions are as follows, noting that some exceptions are observed in each case: (a) The Virial Equation of state (VEOS) to fourth or fifth order describes all properties to within the simulation uncertainty for densities up to at least the critical density,...
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Thermodynamic Properties of Supercritical CO2/CH4 Mixtures from the Virial Equation of State
Journal of Chemical & Engineering Data, 2016Co-Authors: Shu Yang, Andrew J. Schultz, David A. KofkeAbstract:Mixture Virial coefficients to seventh order are presented for the system CO2/CH4 at four supercritical temperatures: 323.15, 373.15, 473.15, and 573.15 K. Values are evaluated via the Mayer sampling Monte Carlo method using a three-site TraPPE model for CO2 and a one-site model for CH4. The coefficients are used to compute seven thermodynamic properties (viz., compressibility factor, isothermal compressibility, volume expansivity, isochoric and isobaric heat capacities, Joule–Thomson coefficient, and speed of sound) as a function of mole fraction and density for these temperatures. Comparison is made with corresponding data in the literature as obtained by molecular dynamics simulation, covering densities up to about twice the critical density. Key conclusions are as follows, noting that some exceptions are observed in each case: (a) The Virial Equation of state (VEOS) to fourth or fifth order describes all properties to within the simulation uncertainty for densities up to at least the critical density,...
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vapor phase metastability and condensation via the Virial Equation of state with extrapolated coefficients
Fluid Phase Equilibria, 2016Co-Authors: Andrew J. Schultz, David A. KofkeAbstract:Abstract Recently reported Virial coefficients for the Lennard-Jones model are extrapolated to very high order, and the results are used to study the behavior of Virial Equation of state (VEOS). Convergence of the VEOS is examined in the context of gas-phase metastability and condensation. Comparison to molecular simulation data shows that the VEOS can accurately describe the Equation of state over much of the metastable region, and the stability limits of very low-order isotherms correspond well with simulation-based estimates of the spinodal densities. However, as higher-order terms are added to the density series, the VEOS becomes less capable of characterizing metastable states, and instead appears to be moving toward a description of condensation. The fully-summed VEOS based on Virial coefficients extrapolated to infinite order abruptly ends in the metastable region with a branch-point singularity. This form represents the culmination of a sequence of curves in which the pressure reaches a maximum before turning downward, both more sharply and at lower density with increasing series order; the corresponding sequence of maxima converge to the point where the fully-summed VEOS diverges. Thus, the extrapolation-based fully-summed VEOS exhibits the qualitative features of condensation, but it fails to provide quantitative agreement with condensation densities established by molecular simulation. The shortcomings point to a need to better understand the behavior of the Virial coefficients with increasing order, perhaps with consideration of the volume dependence of the cluster integrals on which the VEOS is based.
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Modeling solubility in supercritical fluids via the Virial Equation of state
The Journal of Supercritical Fluids, 2010Co-Authors: Andrew J. Schultz, Katherine R. S. Shaul, Shu Yang, David A. KofkeAbstract:We examine the utility of the Virial Equation of state (VEOS) for the prediction of the solubility of hexane in supercritical carbon dioxide. We computed Virial coefficients up to fourth-order for this mixture at 353.15 K, using Mayer-sampling Monte Carlo applied to established molecular models for carbon dioxide and hexane. At this temperature, neither the third- nor fourth-order VEOS indicate the presence of a critical point for the mixture. However, the VEOS coupled with an ideal-solution treatment for the coexisting subcritical fluid phase (with parameters determined from coexistence data at one pressure) reproduces much of the solubility curve as previously established by Gibbs-ensemble molecular simulation. Comparison of the third- and fourth-order VEOS indicate that the Virial treatment is converged at the conditions where it is applied.
Andrew J. Schultz - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic properties of supercritical co2 ch4 mixtures from the Virial Equation of state
Journal of Chemical & Engineering Data, 2016Co-Authors: Shu Yang, Andrew J. Schultz, David A. KofkeAbstract:Mixture Virial coefficients to seventh order are presented for the system CO2/CH4 at four supercritical temperatures: 323.15, 373.15, 473.15, and 573.15 K. Values are evaluated via the Mayer sampling Monte Carlo method using a three-site TraPPE model for CO2 and a one-site model for CH4. The coefficients are used to compute seven thermodynamic properties (viz., compressibility factor, isothermal compressibility, volume expansivity, isochoric and isobaric heat capacities, Joule–Thomson coefficient, and speed of sound) as a function of mole fraction and density for these temperatures. Comparison is made with corresponding data in the literature as obtained by molecular dynamics simulation, covering densities up to about twice the critical density. Key conclusions are as follows, noting that some exceptions are observed in each case: (a) The Virial Equation of state (VEOS) to fourth or fifth order describes all properties to within the simulation uncertainty for densities up to at least the critical density,...
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Thermodynamic Properties of Supercritical CO2/CH4 Mixtures from the Virial Equation of State
Journal of Chemical & Engineering Data, 2016Co-Authors: Shu Yang, Andrew J. Schultz, David A. KofkeAbstract:Mixture Virial coefficients to seventh order are presented for the system CO2/CH4 at four supercritical temperatures: 323.15, 373.15, 473.15, and 573.15 K. Values are evaluated via the Mayer sampling Monte Carlo method using a three-site TraPPE model for CO2 and a one-site model for CH4. The coefficients are used to compute seven thermodynamic properties (viz., compressibility factor, isothermal compressibility, volume expansivity, isochoric and isobaric heat capacities, Joule–Thomson coefficient, and speed of sound) as a function of mole fraction and density for these temperatures. Comparison is made with corresponding data in the literature as obtained by molecular dynamics simulation, covering densities up to about twice the critical density. Key conclusions are as follows, noting that some exceptions are observed in each case: (a) The Virial Equation of state (VEOS) to fourth or fifth order describes all properties to within the simulation uncertainty for densities up to at least the critical density,...
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vapor phase metastability and condensation via the Virial Equation of state with extrapolated coefficients
Fluid Phase Equilibria, 2016Co-Authors: Andrew J. Schultz, David A. KofkeAbstract:Abstract Recently reported Virial coefficients for the Lennard-Jones model are extrapolated to very high order, and the results are used to study the behavior of Virial Equation of state (VEOS). Convergence of the VEOS is examined in the context of gas-phase metastability and condensation. Comparison to molecular simulation data shows that the VEOS can accurately describe the Equation of state over much of the metastable region, and the stability limits of very low-order isotherms correspond well with simulation-based estimates of the spinodal densities. However, as higher-order terms are added to the density series, the VEOS becomes less capable of characterizing metastable states, and instead appears to be moving toward a description of condensation. The fully-summed VEOS based on Virial coefficients extrapolated to infinite order abruptly ends in the metastable region with a branch-point singularity. This form represents the culmination of a sequence of curves in which the pressure reaches a maximum before turning downward, both more sharply and at lower density with increasing series order; the corresponding sequence of maxima converge to the point where the fully-summed VEOS diverges. Thus, the extrapolation-based fully-summed VEOS exhibits the qualitative features of condensation, but it fails to provide quantitative agreement with condensation densities established by molecular simulation. The shortcomings point to a need to better understand the behavior of the Virial coefficients with increasing order, perhaps with consideration of the volume dependence of the cluster integrals on which the VEOS is based.
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Modeling solubility in supercritical fluids via the Virial Equation of state
The Journal of Supercritical Fluids, 2010Co-Authors: Andrew J. Schultz, Katherine R. S. Shaul, Shu Yang, David A. KofkeAbstract:We examine the utility of the Virial Equation of state (VEOS) for the prediction of the solubility of hexane in supercritical carbon dioxide. We computed Virial coefficients up to fourth-order for this mixture at 353.15 K, using Mayer-sampling Monte Carlo applied to established molecular models for carbon dioxide and hexane. At this temperature, neither the third- nor fourth-order VEOS indicate the presence of a critical point for the mixture. However, the VEOS coupled with an ideal-solution treatment for the coexisting subcritical fluid phase (with parameters determined from coexistence data at one pressure) reproduces much of the solubility curve as previously established by Gibbs-ensemble molecular simulation. Comparison of the third- and fourth-order VEOS indicate that the Virial treatment is converged at the conditions where it is applied.
Shu Yang - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic properties of supercritical co2 ch4 mixtures from the Virial Equation of state
Journal of Chemical & Engineering Data, 2016Co-Authors: Shu Yang, Andrew J. Schultz, David A. KofkeAbstract:Mixture Virial coefficients to seventh order are presented for the system CO2/CH4 at four supercritical temperatures: 323.15, 373.15, 473.15, and 573.15 K. Values are evaluated via the Mayer sampling Monte Carlo method using a three-site TraPPE model for CO2 and a one-site model for CH4. The coefficients are used to compute seven thermodynamic properties (viz., compressibility factor, isothermal compressibility, volume expansivity, isochoric and isobaric heat capacities, Joule–Thomson coefficient, and speed of sound) as a function of mole fraction and density for these temperatures. Comparison is made with corresponding data in the literature as obtained by molecular dynamics simulation, covering densities up to about twice the critical density. Key conclusions are as follows, noting that some exceptions are observed in each case: (a) The Virial Equation of state (VEOS) to fourth or fifth order describes all properties to within the simulation uncertainty for densities up to at least the critical density,...
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Thermodynamic Properties of Supercritical CO2/CH4 Mixtures from the Virial Equation of State
Journal of Chemical & Engineering Data, 2016Co-Authors: Shu Yang, Andrew J. Schultz, David A. KofkeAbstract:Mixture Virial coefficients to seventh order are presented for the system CO2/CH4 at four supercritical temperatures: 323.15, 373.15, 473.15, and 573.15 K. Values are evaluated via the Mayer sampling Monte Carlo method using a three-site TraPPE model for CO2 and a one-site model for CH4. The coefficients are used to compute seven thermodynamic properties (viz., compressibility factor, isothermal compressibility, volume expansivity, isochoric and isobaric heat capacities, Joule–Thomson coefficient, and speed of sound) as a function of mole fraction and density for these temperatures. Comparison is made with corresponding data in the literature as obtained by molecular dynamics simulation, covering densities up to about twice the critical density. Key conclusions are as follows, noting that some exceptions are observed in each case: (a) The Virial Equation of state (VEOS) to fourth or fifth order describes all properties to within the simulation uncertainty for densities up to at least the critical density,...
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Modeling solubility in supercritical fluids via the Virial Equation of state
The Journal of Supercritical Fluids, 2010Co-Authors: Andrew J. Schultz, Katherine R. S. Shaul, Shu Yang, David A. KofkeAbstract:We examine the utility of the Virial Equation of state (VEOS) for the prediction of the solubility of hexane in supercritical carbon dioxide. We computed Virial coefficients up to fourth-order for this mixture at 353.15 K, using Mayer-sampling Monte Carlo applied to established molecular models for carbon dioxide and hexane. At this temperature, neither the third- nor fourth-order VEOS indicate the presence of a critical point for the mixture. However, the VEOS coupled with an ideal-solution treatment for the coexisting subcritical fluid phase (with parameters determined from coexistence data at one pressure) reproduces much of the solubility curve as previously established by Gibbs-ensemble molecular simulation. Comparison of the third- and fourth-order VEOS indicate that the Virial treatment is converged at the conditions where it is applied.
M Stumpf - One of the best experts on this subject based on the ideXlab platform.
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Derivation of the Consistent Osmotic Virial Equation and Its Application to Aqueous Poly(ethylene glycol)-Dextran Two-Phase Systems
Macromolecules, 1995Co-Authors: Frank Doebert, Andreas Pfennig, M StumpfAbstract:Based on the osmotic Virial Equation by McMillan and Mayer, thermodynamically consistent expressions for the Gibbs free energy of mixing and the chemical potentials of the solutes are derived. In this derivation the concentration dependence of the specific volume is accounted for explicitly. The omostic Virial coefficients are determined from water-activity data in binary and ternary solutions of poly(ethylene glycol) and dextran of various molecular weights. This consistent osmotic Virial Equation is then tested to predict the liquid-liquid equilibria of the ternary systems. On the basis of the parameters obtained solely from water activities the concentrations as well as the molecular-weight distributions of the polymers in the coexisting liquid phases of the aqueous two-phase systems can be predicted in good agreement with the experimental data.
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Thermodynamics of aqueous poly(ethylene glycol)-dextran two-phase systems using the consistent osmotic Virial Equation
Fluid Phase Equilibria, 1993Co-Authors: Johann Gaube, Andreas Pfennig, M StumpfAbstract:Abstract In this work we present a thermodynamic model for the prediction of the liquid-liquid phase behavior of aqueous poly(ethylene glycol) (PEG) - dextran two-phase systems. The model is based on the McMillan-Mayer solution theory (1945) and results in thermodynamically consistent expressions for the chemical potentials of the solutes derived from the osmotic Virial Equation (COVE). Applying the COVE, we have examined the predictability using a complete and reliable data- base of liquid-liquid equilibrium (LLE) and vapor-liquid equilibrium (VLE) data. As a result of this examination, we were able to demonstrate the essential influence of the molecular-weight distribution of polydisperse polymers on the LLE predictions. Accounting for the polydispersity in our calculations, the prediction of the compositions as well as the molecular-weight distributions in the coexisting phases is in good agreement with our experimental results, as illustrated for the system PEG 3000 + dextran 110000 + water at 293.15 K. It should be stressed, that these calculations are true predictions, since the LLE were calculated using model parameters determined from VLE measurements alone.
Andreas Pfennig - One of the best experts on this subject based on the ideXlab platform.
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Derivation of the Consistent Osmotic Virial Equation and Its Application to Aqueous Poly(ethylene glycol)-Dextran Two-Phase Systems
Macromolecules, 1995Co-Authors: Frank Doebert, Andreas Pfennig, M StumpfAbstract:Based on the osmotic Virial Equation by McMillan and Mayer, thermodynamically consistent expressions for the Gibbs free energy of mixing and the chemical potentials of the solutes are derived. In this derivation the concentration dependence of the specific volume is accounted for explicitly. The omostic Virial coefficients are determined from water-activity data in binary and ternary solutions of poly(ethylene glycol) and dextran of various molecular weights. This consistent osmotic Virial Equation is then tested to predict the liquid-liquid equilibria of the ternary systems. On the basis of the parameters obtained solely from water activities the concentrations as well as the molecular-weight distributions of the polymers in the coexisting liquid phases of the aqueous two-phase systems can be predicted in good agreement with the experimental data.
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Thermodynamics of aqueous poly(ethylene glycol)-dextran two-phase systems using the consistent osmotic Virial Equation
Fluid Phase Equilibria, 1993Co-Authors: Johann Gaube, Andreas Pfennig, M StumpfAbstract:Abstract In this work we present a thermodynamic model for the prediction of the liquid-liquid phase behavior of aqueous poly(ethylene glycol) (PEG) - dextran two-phase systems. The model is based on the McMillan-Mayer solution theory (1945) and results in thermodynamically consistent expressions for the chemical potentials of the solutes derived from the osmotic Virial Equation (COVE). Applying the COVE, we have examined the predictability using a complete and reliable data- base of liquid-liquid equilibrium (LLE) and vapor-liquid equilibrium (VLE) data. As a result of this examination, we were able to demonstrate the essential influence of the molecular-weight distribution of polydisperse polymers on the LLE predictions. Accounting for the polydispersity in our calculations, the prediction of the compositions as well as the molecular-weight distributions in the coexisting phases is in good agreement with our experimental results, as illustrated for the system PEG 3000 + dextran 110000 + water at 293.15 K. It should be stressed, that these calculations are true predictions, since the LLE were calculated using model parameters determined from VLE measurements alone.
